Plaxiphom.] AMPHINEURA. 19 



anterior half of the central valves ; head valve with a brown spot on 

 the umbo, and a few concentric brown lines near the anterior margin ; 

 tail valve the same colouring as the central valves. Interior white, 

 the anterior valve with 8 slits, intermediate valves with 1 slit on each 

 side, posterior valve without slits ; sutural laminse not wide, separated 

 only by a very obtuse sinus. 



Length, 45 mm. ; breadth, 31 mm. Divergence, 140-150. The 

 largest specimen I found measured 60 mm. by 40 mm. 



Type in Mus. Hist. Nat., Paris. 



Hnb. French Pass (type) ; Cook Strait ; Te Onepoto, near Sumner. 



Remarks. This species is rare and local. It is found near low- 

 water mark, on rocks in exposed situations, and mostly hidden between 

 seaweeds. As the Chiton is almost always covered by Nulliporites and 

 seaweeds, it is not easy to see it. The colour is subject to great varia- 

 tion, but green and red-brown are always predominating. The pos- 

 terior fissure of the girdle has formerly been overlooked ; very often 

 it is extending to the tail valve, as in Lorica, but not affecting the valve 

 in any way. Sometimes this fissure is reduced to a simple notch. 



Pilsbry makes P. superba, Carpenter, MS., a synonym of P. bira- 

 mosa, but I cannot share his opinion. Carpenter's species is identical 

 with the very variable P. subatrata, Sut. Mr. E. A. Smith, of the 

 British Museum, kindly sent me a photograph of the type of the 

 former, and there is not the least doubt that the two are conspecific. 



3. Plaxiphora caelata, Reeve, 1847. Plate 2, fig. 5. 



Chiton ccelatus. Reeve, Conch. Icon.. Chiton, pi. 17, f. 101. Plaxiphoia 

 ccelaia, Reeve. Man. Conch. (1), xiv, 328, pi. 58, f. 21. 22; P. Mai. S., 

 ii, 189. Tonicia ziczac, Button, T. N.Z.I., iv, 180. Chiton (Plaxiphora) 

 terminalis, E. A. Smith, Ereb. & Ter.. 4, pi. i, f. 13; Man. Conch. (1), 

 xiv, 326, pi. 51, f. 14. CJuetopleura Hahni, Rochebrune : Wissel, Zool. 

 Jahrb., Syst., xx. 600. pi. 21, f. 12 : pi. 22, f. 13-15 (anatomy); not of 

 Rochebrune. 



Shell elongately oval, roundly angled along the top of the valves, 

 mostly dark brown or black with white markings, girdle hairy. An- 

 terior valve radiately 8-ribbed, with diverging oblique striations on 

 each side of them. Intermediate valves mucronated, the whole surface 

 covered with distinct wrinkles, stouter in front of the lateral areas, 

 diverging from both sides of the jugum, and like the webs from the 

 shaft of a feather from the lateral areas, which are but little raised, 

 with a high radiating nodulous rib in front, and 1 along the suture, 

 which bears coarse concentric lamella? near the margin ; sutures 

 crenulated. Posterior valve with concentric wrinkles, the mucro 

 posterior, with a smooth triangular space in front. Girdle covered 

 with rather sparse brown horny bristles, and with distinct sutural 

 pores. Colour mostly brown, black, or bluish-black, with a white 

 wedge-shaped stripe with a black one within it down the centre of the 

 valves, sometimes a few short white dashes diverging from the radiating 

 ridges ; very rarely ornamented with green and pink. Interior light 



